The long-term goal of this research is to study the development and function of cognitive processes by producing explicit simulations of the behaviors from which the processes are inferred. All components of the simulations will be trained in young children as explicit, overt responses. The stimulus relations that control these components will be made equally explicit by training them with errorless discrimination procedures. The use of overt responses in the simulation will reveal something about the nature of the components necessary for a particular complex behavior to occur, and the precise stimulus control afforded by erroless training will show how thesecomponents must interact. The entire simulation will provide a complex behavior in a form in which its inner workings are directly measurable. Starting from prior research, the experiments will proceed by combining and modifying previously studied components to produce a series of performances involving increasingly more abstract relations. The first experiment will develop identify matching to sample and two forms of oddity matching -- all differing in specifically identifiable features. The effect of these differences on generalization will be demonstrated empirically. In the second experiment, identity matching and one form of oddity will be brought under stimulus control to produce an explicit form of instructional control over two matching- strategies. Properties of stimulus control behavior necessary for the generalization of instructional control will then be explored. The final three experiments will study a component which compensates for the absence of a specified matching stimulus and leads to the selection of a substitute appropriate to the current matching relation. Research will look at the conditions necessary to train this component, integrate it into previously existing behaviors and foster its generalization to novel stimuli in order to simulate a highly abstract level of behavior. The explicit training procedures will have two additional uses. First, they will help identify corresponding contingencies in the natural environment and thereby support the validity of the simulations as copies naturally occurring phenomena. Second, they will provide explicit remedial techniques for both the normal population and the developmentally disabled.